Pipes and tubular conduits – Repairing – Patches
Reexamination Certificate
1999-02-23
2001-03-06
Brinson, Patrick (Department: 3752)
Pipes and tubular conduits
Repairing
Patches
C138S097000, C156S294000, C264S516000
Reexamination Certificate
active
06196271
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to the reconstruction of buried damaged conduits and pipelines, in particular sewers, and more specifically to a liner hose for use in such reconstruction and a method of manufacturing such a liner hose.
In the reconstruction of damaged buried conduits or pipelines such as sewers it has become customary practice to draw a flexible collapsed liner hose comprising at least one layer impregnated with a curable resin through a length of the damaged conduit or pipeline followed by internal expansion of the liner to a desired tubular form matching the walls of the conduit or pipeline and exposing the interior of the liner hose to a curing agent, typically hot water or steam, which is introduced into the hose length to fill it from one end to the other and retained in the hose for a curing period of a duration sufficient to expand the hose to contact the walls of the conduit or pipeline and cure the resin. Alternatively, curing may be effected after expansion of the collapsed hose to form a tubular liner by exposure of the liner to ultraviolet radiation.
Thereby a solid and rigid lining, which is also resistant to the typically aggressive fluid matter carried through the conduit or pipeline, is established inside the damaged conduit or pipeline and complete renewal of the conduit or pipeline itself and the extensive expenses in connection therewith are avoided.
Numerous examples of liner hoses for such conduit reconstruction have been disclosed or suggested in the prior art.
In traditional liner hoses a single layer or overlapping layers of impregnated material, typically felt, fleece or other impregnatable material are confined between inner and outer layers of water-tight plastic film and formed into a hose by joining opposed longitudinal edges of the layer structure into a seam by welding or other appropriate methods. Such hoses have generally suffered from the disadvantage that they only fit one specific conduit or pipeline diameter.
Liner hoses of this traditional type have been disclosed e.g. in GB patent No 1,340,068.
In most cases, the damaged conduit or pipeline to be reconstructed will exhibit more or less significant local irregularities from the ideal circular cross-sectional profile and, if no countermeasures are taken, such irregularities may result in formation of an annular clearance between the external side of the liner hose and the walls of the conduit or pipeline with a resulting risk of penetration of water from the outside into such clearances.
In order to adapt liners hoses to provide a tight engagement with the wall of the conduit or pipeline some prior art solutions, e.g. as disclosed in European Patent Application No. 0 863 359, have prescribed the use of fibrous layers having significant elastic stretchability in the circumferential direction, up to 15 percent.
Such a stretchability results in the disadvantage, however, that uncontrollable variation in the wall thickness of the liner hose may occur. In order to counteract this disadvantage, it is suggested in the European Patent Application quoted above to use intermediate layers which overlap each other and are firmly bonded together in the overlap sections.
Other prior art solutions such as disclosed in German Patent Application No. 41 13 002 and German Patent No. 44 27 663, have suggested the use of overlapping intermediate layers which are not bonded together in the overlap sections, so that a certain stretching of the hose structure in the circumferential direction is made possible through displacement of such overlapping layers with respect to each other. In general, it has been prescribed for such solutions that the overlap sections must be uniformly distributed throughout the circumferential length of the liner profile.
Thereby, the individual fibrous layers may be prepared substantially without circumferential stretchability from fibres orientated mainly in the circumferential or transverse direction resulting in a very high circumferential rigidity of the liner after curing of the resin. In the attempts to reach a maximum of circumferential rigidity it has been disregarded, however, that by use of a general fibre orientation in the circumferential direction longitudinal stretchability of the liner hose may result, whereby local stretching may occur, when a liner hose of significant length is drawn through a damaged conduit or pipeline.
Moreover, all the prior art solutions in respect of using overlapping intermediate layers, whether bonded of unbonded in the overlap sections, have suffered from the disadvantage of a rather complicated manufacturing process requiring a separate folding step for each intermediate layer and a complicated impregnation process.
BRIEF SUMMARY OF THE INVENTION
On the background described above it is the object of the invention to provide a further improvement of liner hoses for conduit and pipe line reconstruction of the kind comprising a number of overlapping intermediate layers, which are unbonded in the overlap sections.
In particular, it is the object of the invention to provide such a liner hose having intermediate layers which are substantially unstretchable both in the transverse direction and the longitudinal direction and can be manufactured at comparatively low costs by a process offering significant simplification with respect to prior art liners.
According to the invention, a liner hose for use in the reconstruction of damaged buried conduits or pipelines, in particular sewers, is provided, comprising inner and outer layers of liquid-tight plastic film material and a number of substantially uniform intermediate layers composed at least partially of a fibrous material impregnated with a curable resin, said liner hose being adapted for introduction into a damaged conduit or pipeline in a collapsed folded condition, followed by expansion of the hose to a substantially tubular structure lining the conduit or pipeline in contact with the walls thereof and curing of said curable resin by introduction of a curing agent into the conduit defined by said inner layer throughout the length of the hose, each of said intermediate layers being formed from a strip, which is substantially unstretchable in any direction and has a width such as to enable folding of the strip into a closed hose structure of the intermediate layer by unbonded seamless overlapping of opposed longitudinal edge zones of said strip in an overlap section, the overlap sections of said number of intermediate layers being all located with mutual separation in the same side of the liner in said folded condition.
By the location of the overlap sections of all intermediate layers in the same side of the liner in its folded condition a significant simplification of the manufacturing process is made possible, whereby all intermediate layers can be folded in a single process step.
The use of intermediate layers, which are substantially uniform in structure throughout the wall thickness of the liner hose, provides a very homogenous structure, by which liner hoses in different dimensions can be prepared from a varying number of a single basic type of intermediate layer. Thereby, also a further contribution is made to simplification of the manufacturing process.
Accordingly, the invention also provides a method of manufacturing the liner hose as defined, for use in the reconstruction of damaged, buried conduits or pipelines, in particular sewers, comprising the steps of arranging a number of said strips into a sandwich configuration in which the strips overlap each other with such a mutual substantially uniform displacement of corresponding longitudinal edges of adjoining strips in said transverse direction substantially at right angles to said longitudinal edges, that the total separation of said longitudinal edges of lower and upper extreme strips in said configuration is less than half the width of each strip, folding said sandwich configuration around said inner hose in a single operation into an intermediate hose form with unbonded seamless overlappi
Braun Michael
Rump Bent Jorgen
Brinson Patrick
Browdy and Neimark
LandOfFree
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